Tobacco use and physical inactivity are the leading causes of preventable death in the United States, accounting for approximately one-third of annual deaths. They also tend to co-exist and apparently influence each other, as persistent smokers are more likely to remain inactive. Despite the widespread dangers associated with tobacco use, the seven-year decreasing trend in the U.S. smoking rate appears to have stalled: 20.8% of adults remained self-reported current smokers in 2006. Although 30-50% of smokers attempt to quit each year, most relapse within three months. These statistics suggest that mainstream cessation assistance options do not work well for many smokers, who may benefit from innovative, alternative cessation treatments. While smoking has been recognized as a leading behavioral risk factor for decades, inactivity has emerged relatively recently as an epidemic of Western society. In 2005, only 29.7% of the adult population reportedly engaged in regular leisure-time physical activity, and 10.3% obtained less than ten minutes of moderate or vigorous intensity physical activity per week. PUBLIC HEALTH RELEVANCE: The proposed study addresses both of these major public health problems, as it attempts to replace an unhealthy, addictive behavior (smoking) with a healthy, yet still rewarding activity (exercise). Inactive adult smokers who desire to quit and are otherwise generally healthy will be eligible to participate. The few previous studies attempting to replace smoking with exercise have resulted in modest, short-term smoking cessation success comparable to conventional cessation methods. The proposed study adds unique intervention strategies, including an exercise protocol that capitalizes on the frequent nicotine cravingsthat smokers experience during quit attempts and the craving reductions that occur during and after exercise;an Internet-based standard care control group;and other notable measurement components, to the methods employed in prior studies. The primary goal of the proposed study is to help smokers who desire to quit achieve both short- and long-term cessation, regardless of whether they are randomly assigned to the intervention or control group. Specific aims include examining the effectiveness of short bouts of exercise in response to cigarette cravings in terms of exercise compliance, smoking cessation success, prevention of weight gain, and improvements in fitness. Inactive smokers who desire to quit will have the opportunity to receive a free online smoking cessation program, and some will also receive an exercise training plan to follow in attempt to replace their unhealthy addiction with a healthy activity. This study is consistent with NIDA's recently identified goal of developing exercise interventions for substance abuse/addictions.